From scratch... start with the basics, HTML (definitely first), Scripting Language (PHP/Python/whatever), bits of javascript. Don't jump into CSS too early, it just messes with your brain (its very anti-logic compared to HTML and scripting languages). Once you are confident in the scripting add in a database if that's your thing. Once you are adept at getting data in and out from the server then look into prettifying things up with CSS.

A good beginning reference for CSS is "Stylin' with CSS: A Designer's Guide" by Charles Wyke-Smith, good basics. Problem with CSS is there is a lot of crap overload out there mainly because of browser variation - strive to find the simpler solutions.